Phages of Streptococcus pneumonaie (pneumococcus) and their DNA will be used in conjunction with transformation and plasmids to analyze genetic processes in this species. So far the repertory of genetic assays has been expanded from transformation to include phage recombination, several forms of transfection, and a novel form of generalized transduction. At least one plasmid has recently been found and is being studied. Also, two previously unknown guanine derivatives have been found in lytic phage DNAs, and they affect the DNA properties in significant ways, including susceptibility to sequence-specific nucelases. Work will continue on mechanisms of transfection and transduction, and on the unusual nucleotides. New lines of investigation will be directed at thorough characterization of a temperate phage system, at examining plasmids in pneumococcus, and beginning a search for insertion sequences, using the above as tools. With transformation and these elements as background, the organization and possible orgins of newly appearing multiple drug-resistance geneses in clinical isolates will be examined.